So called performance enhancers are often used when feeding of animals is concerned. These substances optimize the nutrient uptake in rumen and intestine. This way, feed conversion is improved and the consummation per kilogram weight gain is reduced. As far as performance enhancers are concerned, a distinction is drawn between antibiotic, probiotic and chemical performance enhancers.
Lately, the use of performance enhancers, particularly of antibiotic and chemical performance enhancers, has become less accepted by the consumers, but also by some of those skilled in the art, since on the one hand people worry about negative effects on human health caused by residues of the substances used in food of animal origin, and on the other hand people are afraid of developing resistance to microorganisms, particularly to human pathogenic organisms. Also, in some countries many of the substances used as performance enhancers are no longer allowed to be used as feed additives.
On the other hand, it has to be noted that many livestock owners are in favor of the use of performance enhancers, since these substances not only enhance animal growth but can also improve the state of health of the animals. Thus, main attention is now turned to the research on suitable substitutes, such that conventional performance enhancers can be replaced by alternative ones.
The use of benzophenanthridine alkaloids for performance enhancement is known from DE 43 03 099. These alkaloids are particularly contained in Sanguinaria canadensis, which, however, is a natural plant material and thus is only available in limited amounts. Thus, these alkaloids are comparatively expensive.
From WO 02/21933 the use of a protoberberine alkaloid in combination with a benzophenanthridine alkaloid as performance enhancer or appetite stimulant for livestock is known.